As the flow rate measurement device of this type, a flow rate measurement device having an ultrasonic transmission film disposed between ultrasonic transceivers and a measurement channel is conventionally known (see Patent Literature 1, for example).
FIG. 6 is an exploded perspective view of a flow rate measurement device disclosed in Patent Literature 1.
As illustrated in FIG. 6, flow rate measurement device 101 includes channel body 102 and sensor block 103.
Channel body 102 includes measurement channel 104 having a rectangular cross section. Measurement channel 104 is divided into a plurality of flat channels by a plurality of partition plates 105.
First ultrasonic transceiver 106 and second ultrasonic transceiver 107 are attached to sensor block 103. An ultrasonic transmission film 108 is disposed between measurement channel 104 and first and second ultrasonic transceivers 106 and 107. Ultrasonic transmission film 108 is formed as a single piece using a mesh material, for example.
FIG. 7 is a vertical cross section of flow rate measurement device 101 illustrated in FIG. 6, taken along a plane along the flow direction.
As illustrated in FIG. 7, first hole portion 109 is formed between first ultrasonic transceiver 106 and measurement channel 104, and second hole portion 110 is formed between second ultrasonic transceiver 107 and measurement channel 104. Ultrasonic transmission film 108 is disposed between first hole portion 109 and measurement channel 104 and between second hole portion 110 and measurement channel 104, and reduces the occurrence of turbulence caused by entrained flows in first hole portion 109 and second hole portion 110.
In this configuration, ultrasound emitted from first ultrasonic transceiver 106 passes through ultrasonic transmission film 108 via first hole portion 109, and then travels into measurement channel 104 and is reflected at bottom surface 111 of measurement channel 104. After that, the ultrasound passes through ultrasonic transmission film 108 again, and reaches second ultrasonic transceiver 107 via second hole portion 110. The flow rate of a fluid passing through measurement channel 104 is measured based on a propagation time it takes for the ultrasound emitted from first ultrasonic transceiver 106 to reach second ultrasonic transceiver 107.